Means for obtaining high-voltage electrical impulses



Jim. 14, 1930. N. w. MOLACHLAN 1,743,152

MEANS FOR OBTAINING HIGH VOLTAGE ELECTRICAL INPULSES Filed Feb. 25. 1922 avwentoz NOR AN WM LACHLAN 351;; M5 abtmegz d f M Patented Jan. 14,1930

UNITED STATES PATENT oFnca NORMAL WELIAI ICLAOHIJAN, OF NEWCASTLE-UPON-THE-TYNE, ENGLAND, A S- SIGNOR TO RADIO CORPORATION OF AMERICA, A CORPORATION 01 DELAWARE MEANS FOR OBTAINING HIGH-VOLTAGE ELECTRICAL IMPULSES Application filed February 25, 1922, Serial No.

- The object of this invention is to provide improved means for obtaining electrical impulses of high voltage.

According to this invention I connect in the anode circuit of a triode or three-electrode valve a coil of large inductance and a source of direct current and I provide means for imparting to the grid of the valve 8. high negative potential with respect to the negative end of the filament whereby the resistance of the valve is suddenly made very large so that the difference of potential between the ends of the coil is suddenly increased. If therefore a spark gap, X ray bulb or'other like device be connected across the coil a spark or discharge will be produced.

Preferably the anode is connected to one end of the coil, the other end of which is connected to the positive terminal of a source of direct current, e. g. a'direct current dynamo or .a rectifiedalternating current, the negative terminal of which is connected to the negative terminalof the filament batter In order to increase the current in the ano e circuit before the negative potential is applied to the grid the latter is made positive.

If suitable means are used to make the grid alternately positive and negative-with regard to the negative end of the filament a succession of sparks will occur at the spark gap.

If'the grid is made sufiici'ently negat ve n respect to the filament, the rate of rise of potential on the terminals of the coil depends on its inductance, its distributed capacity and the current flowing therein when the resistance of the valve is suddenly increased. By making the inductance large, the distributed capacit small and the current of suitable value, t e rate ofrise of potential may 'be made very large.

The invention isillustrated by the single figure of the accompanying diagram, in which Q, is an air or iron coredcoll of'high inductance connected in series with a d1rect current dynamo D in the anode circuit of a three electrode valve V. Across Q is connected a spark gap or an X-ray bulb S, through which it is desired to obtain a pulse of cur-- rent. The grid of the valve V is connected to acontact of an interruptor Y to the outer 538,160, and in Great Britain April 30, 1921.

contacts X, Z, of which are connected direct current dynamos D D Any appropriate mechanical or electrical means I ma be utilized to connect Y alternately to and Z. The common point of D D is connected to the filament of the valve and may be earthed if desired. 'When Y and Z are connected and Y and X insulated from each other, the potential of the grid is positive with respect to the filament. This causes the valve to become highly conductive and a current flows in the anode circuit through coil Q. Whenconnection to Y has moved over from Z to X, the grid'is made highly negative with regard to the filament, and the conductivity of the valve is practically reduced to zero. In order to establish the positive and negative potentials on the grid as rapidly as possible, condensers C and G are connected across D and D respectively.

Condenser C? is to shunt any oscillatory current which would otherwise flow across coil Q to increase rapidly and reach' such a value that a discharge occurs at S. If the conductivity of the valve is zero, and there is no leak across S, the rate of rise of voltage across Q, for any given flux interlinkage depends on its inductance and self-capacity. The rate of rise for any given flux interhnkage can be increased by reducing the inductance and self-capacity or both, and decreased by increasing either one or both of these quantities. It can also be decreased for any given flux inter-linkage by connecting a condenser across, the coil; the rate of rise can also be decreased by increasing the conductivity of the valve, i. e. making the negative potential onthe grid smaller. In the latter case the peak voltage across the coil, in the abof rise of potential. If the resistance across the terminals of the coil, i. e. in parallel. is infinite, the coil oscillates freely when the conductivity of the valve is reduced to zero. 5 When, however, the resistance of the device across the coil is not infinite there is a leakage through the device with a consequent loss of energy. The frequency of the oscillations and the damping are modified, and for a certain value of resistance across the coil the circuit becomes aperiodic.

Having described my invention, what I claim is:

In a mechanism for obtaining high voltage impulses a triode having input and output circuits said output circuit comprising a relatively large inductance coil, a source of direct current in series and autilizing circuit in parallel with said inductance coil, a circuit comprising two current sources arranged in series, a pair of capacities in series shunted across said current sources, means for grounding the common portion of both said current sources and said two capacities, a rotating pole changer connected across said two current sources and the grid electrode of said triode and adapted to alternately place a positive and negative charge in said electrode and a connection between the filament of said triode and round.

NORMA WILLIAM MGLACHLAN. 

